Sugar and other water soluble nutrients may be extracted from plant matter. For example, relatively pure sucrose, which is a disaccharide of glucose and fructose and is the primary sugar in sugar cane, may be obtained from sugar cane or sugar beets during a milling and/or pressing process. The extracted sugars may then be refined for later use, for example, as a sweetener, such as table sugar, and/or in alcohol production, such as ethanol. Other sugars and water soluble nutrients, such as glucose, galactose, and fructose, as well as disaccharides thereof, may also be extracted from plant matter, including sugar cane and sugar beets, for example.
Sugar containing plants such as sugar cane have two primary components, a fiber component that forms the structure of the plants, and a liquid component that contains the sugars. The sugar containing liquid component is typically extracted from the fiber component at a sugar mill. At the mill, plants such as the sugar cane stalks, may be washed prior to extraction. The washing step utilizes water to remove dirt and other potential contaminants from the surface of the plants. The plants may be washed such as by spraying or immersing in the water. Routine washing techniques can leave some residual dirt and other contaminants remaining on the plants that can contaminate the extracted sugars and must be removed during the filtering and refining process. Improvements in washing the plants are needed to decrease contamination of the extracted sugars and to improve the refining process.
For sugar cane processing, after washing, the stalks of sugar cane undergo a cane breaking process in which the tough outer covering of the stalks are broken and the cane is ground or crushed into smaller pieces from which the liquid fraction is extracted. The liquid fraction may then be extracted from the ground or crushed cane by combination of pressing and imbibition. Imbibition is a process in which water or previously extracted cane liquid is applied to the ground or crushed cane to enhance the extraction of the sugar containing liquid fraction from the fibrous component during the pressing step. Greater amounts of water used in the imbibitions step typically yields more sugar, but this also creates a more dilute juice and, thus, more energy is required to evaporate the juice in the downstream refining process.
In a typical pressing process, the ground or crushed stalks are exposed to a first pressing to separate the liquid component from fiber component. The left over fiber component is referred to as the bagasse. The collected liquid component from the first pressing may be diluted with water or may be used in its undiluted form and reapplied to the bagasse in an imbibition step to extract additional sugar in a second pressing step. Additional imbibition and pressing steps may be utilized with the bagasse to achieve maximum sugar extraction. Typical extraction methods obtain a cane liquid fraction with around 15% sugar content. Improvements in the milling process are needed that result in a higher concentration of sugar in the extracted liquid.
Sugar mills are large and costly plants that represent significant capital investments. It would be beneficial to improve the yield of sugar and/or other nutrients of interest extracted from sugar cane or other plant materials without requiring significant alterations to existing mill and extraction facilities.